I have an iphone 3gs (OLD bootrom) running 3.1.3 spirit jb with only 3.1.3 SHSH blobs on file. Can I get jailbroken ios4 by doing this: 1. Restore to 3.1.3 non jb using SHSH blobs. 2. Jailbreak using sn0wbreeze 3. Use pwnagetol to upgade to jaibroken iOS 4 Will this work?